1. Field of the Invention
The present invention relates to a method and a system for sampling a gas for both particulate and vapor phase metal impurities. In particular, the system of the present invention is very portable in that it can be easily removed from the site of the gas being sampled and returned to a laboratory for an accurate analysis of the metal impurities trapped in the filters of the system.
2. Brief Description of the Prior Art
A very important and crucial aspect in semi-conductor manufacturing is the constant control of metallic impurities in process gases. Generally, the impurities are present due to corrosion, shedding from values and the like. In order to reduce the metallic impurities in the gases prior to their reaching the semiconductor manufacturing process, the gases flowing through the system must be sampled. Analysis of the gases can indicate whether metallic impurities, being introduced from outside the system or being created inside the system, are contaminating the manufacturing process. The level of detection for metallic impurities in semiconductor manufacture processes must reach the parts per trillion level, and therefore requires very sophisticated equipment for analysis and detection.
Methods for sampling gases in order to detect metallic impurities have applications well beyond the semi-conductor manufacturing industry. In most of the methods used, the gases are hydrolyzable, i.e., dissolvable in water, and therefore hydrolysis is commonly used for sampling the metals in the gases. However, gases such as nitrogen, SiH.sub.4, and CF.sub.4, some of which are commonly used in semi-conductor manufacturing processes, are not hydrolyzable. Therefore, in order to sample the gases and detect metal impurities in the gases, a filtering system must be used.
To render such a filtering system most useful for the industry, it must be very efficient and effective for measuring and detecting metallic impurities to the parts per trillion level. Efficiency in such detection often requires the most sophisticated of analysis equipment, and therefore it would also be most desirable if such a filtering system were portable so that it can be easily transported to a laboratory where access to the necessary analysis equipment can be had.
Accordingly, it is an object of the present invention to provide a sampling system and method for using such a system to sample non hydrolyzable gases and analyze the gases for metal impurities.
It is another object of the present invention to provide methods and systems to sample non-hydrolyzable gases for both particulate and vapor phase metallic impurities in an effective and efficient manner.
It is yet another object of the present invention to provide a portable system for sampling non-hydrolyzable gases for the ultimate detection of metallic impurities so that the sophisticated analysis equipment typically required can be easily used at an off-site laboratory.
These and other objects of the present invention will become apparent upon a review of the following specification, the FIGURE of the Drawing, and the claims appended hereto.